Aspects of the design, production and use of biological switches based on ligand-mediated multimerization of immunophilin-based recombinant proteins are disclosed in Spencer et al, Nov. 12, 1993, Science 262:1019-1024 and in International Patent Applications PCT/US94/01660 and PCT/US94/08008. One class of multimerizing agents is based on dimers of the macrocyclic natural product, FK506, covalently attached to each other via a synthetic linker moiety. The resultant dimers ("FK1012" molecules) are characterized by high binding affinities for immunophilin molecules. However, they are large, complex molecules which can be inconvenient to produce. New methods and materials for multimerizing chimeric proteins containing immunophilin moieties would be desirable, where the methods and materials involve smaller, simpler multimerizing agents which retain a high binding affinity for their coordinate immunophilins, but which are more convenient to produce and are more readily amenable to structural modification.